Debugging tools for software-implemented real time operating systems are well known in the art. One existing debugging tool includes a host debug and a target debug (also referred to as a monitor) that communicate to each other via a network bridge (e.g., a serial bridge, an Ethernet bridge, a shared memory bridge, etc.). In particular, the target debugger receives debugging commands from the host debugger, obtains data requested by the host debugger and sends this data back to the host debugger. The data requested by the host debugger may include status information about a currently running process, information about processes awaiting their turn in a queue, a snapshot of the operating system at the time the command was executed, or any other related information. Typically, in order to extract the requested information, the current operation of the processor has to be stopped. In addition to such intrusiveness, this debugging technique is cumbersome to use because it requires the existence of a network bridge and a target debugging application written for a specific operating system.
Another known debugging technique uses IEEE 1149.1 interface (also known as Joint Test Access Group (JTAG) interface) to enable a host debugger application to interact with a processor and a software-implemented operating system. JTAG is a standard specifying how to control and monitor pins of compliant devices on a printed circuit board. JTAG allows the vendors of debugging tools to provide such testing functionality as external access to memory and registers of the processor, connected to a JTAG port, and the ability to stop and start the code execution. Using JTAG, the host debugger application is provided with information on various components of the computer system (e.g., processor registers, an address bus, a data bus, memory caches, etc.) with no need to have a target-resident debugger application or a network bridge. However, current JTAG-based debugging tools cannot extract the information requested by the host debugger application without interrupting the operation of the processor. In addition, existing JTAG-based debugging techniques do not support hardware-implemented real time operating systems.
Therefore, what is required is a tool to debug a hardware-implemented operating system without disturbing the operation of a processor.